An investigation of titanium dioxide photocatalysis for the treatment of water contaminated with metals and organic chemicals

Prairie, M.R.; Evans, Lindsey; Stange, B.M.; Martinez, S. L.

doi:10.1021/es00046a003

Cited by 353 publications

(186 citation statements)

References 33 publications

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“…[1,2] Nanosized TiO 2 is one of the most widely used photocatalysts among the semiconductors being studied due to its favorable characteristics such as its low cost, good chemical stability, high photocatalytic activity, and nontoxic nature. [3][4][5][6] Although it has been proven that most organic contaminants in water can be effectively mineralized under UV irradiation, efficient recovery of this finely powdered TiO 2 from treated water is still a challenge, which prevents its widespread application. Nanocrystalline TiO 2 immobilized on supporting materials such as glass, sand, or zeolite can improve the separation efficiency.…”

Section: Introductionmentioning

confidence: 99%

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Zhang

et al. 2010

Chemistry A European J

319

203

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Core–shell structured Fe3O4/SiO2/TiO2 nanocomposites with enhanced photocatalytic activity that are capable of fast magnetic separation have been successfully synthesized by combining two steps of a sol–gel process with calcination. The as‐obtained core–shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and an outer layer of TiO2 nanocrystals with a tunable average size. The convenient control over the size and crystallinity of the TiO2 nanocatalysts makes it possible to achieve higher photocatalytic efficiency than that of commercial photocatalyst Degussa P25. The photocatalytic activity increases as the thickness of the TiO2 nanocrystal shell decreases. The presence of SiO2 interlayer helps to enhance the photocatalytic efficiency of the TiO2 nanocrystal shell as well as the chemical and thermal stability of Fe3O4 core. In addition, the TiO2 nanocrystals strongly adhere to the magnetic supports through covalent bonds. We demonstrate that this photocatalyst can be easily recycled by applying an external magnetic field while maintaining their photocatalytic activity during at least eighteen cycles of use.

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Section: Introductionmentioning

confidence: 99%

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Zhang

et al. 2010

Chemistry A European J

319

203

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“…The same source lists a number of common effective hole scavengers. The more commonly used are: methanol and ethanol, 14,20 2-propanol, 20 but also acetic acid, 14,12 salicylic acid and EDTA. 14 The goal of the work accounted in the present article was to show the influence, in the photocatalytic digestion, of species possibly present in solution and capable to trap and consume electrons or positive holes and, thus, to interfere favourably or unfavourably in the oxidation mechanism of organic substrates.…”

Section: Introductionmentioning

confidence: 99%

“…The more commonly used are: methanol and ethanol, 14,20 2-propanol, 20 but also acetic acid, 14,12 salicylic acid and EDTA. 14 The goal of the work accounted in the present article was to show the influence, in the photocatalytic digestion, of species possibly present in solution and capable to trap and consume electrons or positive holes and, thus, to interfere favourably or unfavourably in the oxidation mechanism of organic substrates. Such an investigation, in the first place, intended to incorporate into the previous model system, elements able to turn it a more realistic system, with the possibility of a more reliable prediction of the behaviour of real samples submitted to the analytical treatment.…”

Section: Introductionmentioning

confidence: 99%

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Cavicchioli

Gutz

2002

J. Braz. Chem. Soc.

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A influência de scavengers de elétrons e de lacunas positivas na digestão fotocatalítica de matéria orgânica na presença de partículas de TiO 2 em suspensão, foi investigada. O processo, que visa a determinação eletroquímica de traços de metais pesados em amostras de água, foi acompanhado mediante observação da recuperação da onda voltamétrica de Cd(II) em presença de EDTA, escolhido como ligante-modelo na simulação do efeito complexante da matéria orgânica natural. Confirmouse o poder acelerador de O 2 , que atua como removedor de elétrons. Na ausência de O 2 , função análoga é exercida pelo íon nitrato, mas não, ao menos aparentemente, pelo analito Cd(II). Já a adição de CH 3 OH apresenta efeito antagônico de scavenger de lacunas positivas, o que pode explicar porque a operação na presença de acetato (usado como tampão de pH), ao mesmo tempo em que proporciona um eficaz controle da acidez do meio, provoca uma certa redução do rendimento da fotodegradação.The influence of electron and hole scavengers in the photocatalytic digestion of organic matter in the presence of suspended particles of TiO 2 was investigated. The process, aiming at the electrochemical determination of traces of heavy metals in water samples, was followed through the recovery of the voltammetric wave of Cd(II) in the presence of EDTA, chosen as model ligand that mimics the complexing effect of natural dissolved organic matter. The accelerating power of O 2 , acting as electron scavenger, was confirmed. In the absence of O 2 , a similar function is played by nitrate ions but not, as it seems, by the analyte, Cd(II). On the other hand, CH 3 OH exhibits an antagonist effect as hole scavenger. This observation may explain why the acetate (from the pH buffer), used to control the medium acidity, leads to a certain reduction in the photocatalytic yield.

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“…Hence reactions that either consume h + vb or ecb can enhance the photocatalytic activity of TiO 2 . Molecular O 2 , silver(I), mercury(II), and chromium(VI) have been used in combination with photocatalytic processes (Prairie et al 1993;Linesebigler et al 1995). Iron in its +6 oxidation state, ferrate(VI) (Fe(VI), Fe VI O 4 2-) can serve as an alternative to undesirable (toxic) metal ions to increase the photocatalytic efficiency.…”

Section: Introductionmentioning

confidence: 99%

Ferrate(VI) enhanced photocatalytic oxidation of pollutants in aqueous TiO2 suspensions

Sharma

Graham

et al. 2009

Environ Sci Pollut Res

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Background, aim, and scope Photocatalytic oxidation using UV irradiation of TiO 2 has been studied extensively and has many potential industrial applications, including the degradation of recalcitrant contaminants in water and wastewater treatment. A limiting factor in the oxidation process is the recombination of conduction band electrons (ecb ) with electron holes (h + vb ) on the irradiated TiO 2 surface, thus in aqueous conditions the presence of an effective electron scavenger will be beneficial to the efficiency of the oxidation process. Ferrate (FeO 4 2-) has received much recent attention as a water treatment chemical since it behaves simultaneously as an oxidant and coagulant. The combination of ferrate (Fe(VI)) with UV/TiO 2 photocatalysis offers an oxidation synergism arising from the Fe(VI) scavenging of ecb and the corresponding beneficial formation of Fe(V) from the Fe(VI) reduction. This paper reviews recent studies concerning the photocatalytic oxidation of problematic pollutants with and without ferrate. Materials and methods The paper reviews the published results of laboratory experiments designed to follow the photocatalytic degradation of selected contaminants of environmental significance and the influence of the experimental conditions (eg. pH, reactant concentrations, dissolved oxygen). The specific compounds are as follows: ammonia, cyanate, formic acid, bisphenol-A, dibutyl-and dimethyl-phthalate, and microcystin-LR. The principal focus in these studies has been on the rates of reaction rather than on reaction pathways and products. Results The presence of UV/TiO 2 accelerates the chemical reduction of ferrate and the reduction rate decreases with pH owing to deprotonation of ferrate ion. For all the selected contaminant substances the photocatalytic oxidation rate was greater in the presence of ferrate and this was believed to be synergistic rather than additive. The presence of dissolved oxygen in solution reduced the degradation rate of dimethyl phthalate in the ferrate/photocatalysis system. In the study of microcystin-LR it was evident that an optimal ferrate concentration exists, whereby higher Fe(VI) concentrations above the optimum leads to a reduction in microcystin-LR degradation. In addition, the rate of microcystin-LR degradation was found to be strongly dependent on pH and was greatest at pH 6. Discussion The initial rate of photocatalytic reduction under different conditions was analysed using a Langmuirian form. Decrease in rates in the presence of dissolved oxygen may be due to competition between oxygen and ferrate as electron scavengers, and to non-productive radical species interactions. The reaction between ferrate(VI) and MCLR in the pH range of 6.0-10.0 is most likely controlled by the protonated Fe(VI) species, HFeO 4 -. Conclusions The photocatalytic oxidation of selected, recalcitrant contaminants was found to be significantly greater in the presence of ferrate, arising from the role of ferrate in inhibiting the h + vb -ecb pair recombination on TiO 2 su...

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An investigation of titanium dioxide photocatalysis for the treatment of water contaminated with metals and organic chemicals

Cited by 353 publications

References 33 publications

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Magnetically Recoverable Core–Shell Nanocomposites with Enhanced Photocatalytic Activity

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

Ferrate(VI) enhanced photocatalytic oxidation of pollutants in aqueous TiO2 suspensions

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